Electric arc furnace



Aug. 29, 1939. K. SCHNEIDER El AL 2,171,436

ELECTRIC ARC FURNACE ori inal Filed Jan. 23, 1937 Kurt dc/znecvler Hermann, Schunck lnvemors By 772a) Afforneys Patented Aug. 29, 1939 2,171,436 Emo'rmo ARC FURNACE 7 Kurt Schneider and Herman Schunck, Bitterfeld, Germany, assignors to I.

Aktiengesellschaft,

trie Main, Germany G. Farbenindus- Frankfort-on-the- Original application January 23, 1937, Serial No. 121,988. Divided-and this application January 11, 1939, Serial No. uary 28, 1936 2 Claims.

This invention relates to a method of and means for magnetically blowing electric arcs on metal electrodes and is a divisional application from our copending application Serial No. 121,988

entitled Electric arc furnace and filed January When metal electrodes are employed in electric arc furnaces, it is necessary to cause the points where the arc is struck to migrate over the electrodes, in order to prevent them from fusing under the influence of the temperatures generated at the striking point. This migration can be effected by blowing the arc, by means of a current of gas, by mechanically moving, for example. rotating, 'the electrodes or by generating in the proximity of the arc, a magnetic field energized by direct or alternating current. In thelast-named method however, the generating of said field by means such as electromagnets separated and remote from the electrodes themselves, entails, especially in the case of electric furnaces of the covered type of corresponding modification in the furnace design, in order to accommodate the electromagnets. This imposes limitations on the form of the furnace chamber which are frequently inconvenient or undesirable. On the other hand when the energizing coil is situated outside the shell of the furnace difficulties are encountered in adequately heat-insulating the shell.

The present invention aims at obviating the necessity of providing arc-blowing means separate from the electrodes and the disadvantages consequent thereon, by generating the electromagnetic blowlng field in the electrode itself by means of an electric current circulating round or passing through the electrode. This arrangement, in which the means energising the magnetic field form an integral unit with the electrode, does not in any way interfere with the normal furnace design. For example, in the case of shaft furnaces, the shell may be provided with heat-insulating layers of any convenient thickness, or in the case of drum furnaces, which are particularly favored in view of their thermal economy, such furnaces may be equipped with metal electrodes, which was hitherto considered impossible. Gas-reaction furnaces too, can be of particularly simple design, since the reaction chamber can bedesigned solely with a view to obtaining optimum conditions of flow in the gas space, without havingto take into consideration the restrictions otherwise imposed by. the accommodation of the electromagnetic blowing means.

In order more clearly to understand the inven- 250,302. In Germany Jantion, reference is made to the accompanying drawing which illustrates diagrammatically and by way of example an embodiment thereof.

E1 and E2 designate electrodes of the well known hair-pin design. B and'C denote respectively the inand out-leads for the working current which generates the are L between the electrodes E1 and E2, the path of the current being therefore from B to C via L. Arranged adjacent the open end of each electrode is a transformer W. The primary of said transformer P is provided by lead said lead being connected to'electrode E2 'at D. The secondary of the transformer is designated by S, the secondary being connected to electrode E2 at D1 and F. It will be seen from this arrangement that the applied voltage forces the working current directly through the primary P to the electrode E2. The working current in passing through the primary induces in the secondary 5 an auxiliary current of high strength and very low voltage. Said induced current generates the magnetic field, the lines of force of which are represented by the arrows K on the drawing, said lines of force surrounding the elements, even at the striking points thereof. J

In the event that the source of current supply is direct current, the auxiliary current may be generated by a thermo-element.

If different types of current be employed for the working and energising currents, i. e. direct current as working current and alternating current as energising current or vice versa, the arc will not be extinguished but will travel to and fro 0n the electrode, the resulting are being thus evenly distributed on both sides of the electrode. On the other hand, if direct current, or alternating current, be assume the form of a stationary semi-circular disc. In such case the current energising the electromagnetic field can be generated, in a particularly simple manner as shown in the drawing, in a transformer energised by the working current, and, if alternating current be employed, the correct phase relation between the working current and the energising current is automatically obtained.

When heating solid or liquid substances disposed on the hearth of the furnace, for instance when applying the invention to a horizontal drum furnace, and when the electrodes are arranged horizontally and either only direct, or only alternating, current is used, the semi-circular arc may be directed downwards and may be caused to play directly on the charge material, whilst the ceiling of the'furnace is thus protected. In such case,

exclusively employed, the arc will when the charge to be melted is a conductor, the

' arc is struck not only between the two electrodes,

but also between each electrode and the conducting charge material, whereby a particularly favorable utilisation of energy is assured.

In order to avoid extinction of the are when operating solely with alternating current, alternating currents of difierent frequencies can be employed for the working current and for the energising current, provided thatboth frequencies are in integral proportion and that they have a series of zero points in common.

We claim: I

1. An electric arc furnace comprising two electrodes, at least one of hair-pin design, means forsupplying a working current through and across the gap between said such electrodes being 'of r arm/sec electrodes, a primary coil in the path of said working current and adjacent to said electrode of hair-pin design, a secondary coil inductively 

